Asthma is a serious chronic condition. In the United States alone, it is believed that asthma affects upward of 15 million Americans. Asthma is characterized by (i) bronchoconstriction, (ii) excessive mucus production, and (iii) inflammation and swelling of airways. These conditions cause widespread and variable airflow obstruction thereby making it difficult for the asthma sufferer to breathe. Asthma further includes acute episodes or attacks of additional airway narrowing via contraction of hyper-responsive airway smooth muscle. Other obstructive diseases such as COPD may also have a reversible component caused by one or more of the above mentioned three elements.
Asthma generally includes excessive mucus production in the bronchial tree. Usually, there is a general increase in bulk (hypertrophy) of the large bronchi and chronic inflammatory changes in the small airways. See for example, Hogg, J C. The Pathology of Asthma. APMIS 1997; 105:735-745. Excessive amounts of mucus are found in the airways and semisolid plugs of mucus may occlude some small bronchi. Also, the small airways are narrowed and may show inflammatory changes. See, e.g., Kraft M, The Distal Airways: Are they Important in Asthma? Eur Respir J 1999; 14:1403-1417. The reversible aspects of COPD include partial airway occlusion by excess secretions, bronchial wall edema, inflammation of the airways and airway narrowing as a result of smooth muscle contraction.
The role of airway smooth muscle and its effect in patients with asthma is gaining increased attention in the medical community. See, for example, Shore S, Airway Smooth Muscle in Asthma—Not Just More of the Same, 2004 N Engl J Med 351; 6; Jeffery P K. Remodeling in Asthma and Chronic Obstructive Lung Diseas., Am J. Respir Crit Care Med 2001; 1645: S28-S38; Global Initiative for Asthma (GINA) Global Strategy for Asthma Management and Prevention, NIH/NHLBI, 2002 NIH Publication No 02-3659 Furthermore, the literature tends to support the belief that smooth muscle tissue within the airways is not essential to normal lung physiology and that the smooth muscle tissue may in fact be a vestigial organ. In the case of individuals with asthma, the airway smooth muscle may actually cause medical complications. See, for example, Seow C Y, Fredberg J J, Historical Perspective on Airway Smooth Muscle: the Saga of a Frustrated Cell, 2001 J Appl Physiol 91(2):938-952, Mitzner W, Airway Smooth Muscle: the Appendix of the Lung, 2004 AJRCCM, 169:787-790.
Currently, asthma management includes a combination of stimulus avoidance and pharmacological mediation. Stimulus avoidance includes systematic identification of each type of stimuli and minimization of contact with each type of stimuli. It may, however, be impractical and not always helpful to avoid all potential stimuli.
Pharmacological mediation of asthma includes: (1) long term control through use of anti-inflammatories and long-acting bronchodilators and (2) short term management of acute exacerbations through use of short-acting bronchodilators. Both approaches require repeated and regular use of the prescribed drugs. High doses of corticosteroid anti-inflammatory drugs may include serious side effects requiring careful management. In addition, some patients are resistant to steroid treatment.
The difficulties involved in patient compliance with pharmacologic management and the difficulties of avoiding asthma triggering stimulus are common barriers to successful asthma management. It follows that current management techniques are neither completely successful nor free from side effects. Aside from the difficulties in these management techniques, some individuals may seek a more permanent solution to manage asthma.
Removal and/or deactivation of a body organ, vestigial or not, is medically acceptable as long as there is an overall benefit. A few examples of such procedures include removal of: body hair, the appendix, wisdom teeth, and portions of the cornea. Moreover, deactivation of certain muscles is accepted for cosmetic results. In this latter procedure, a physician injects botulism toxin type A (i.e., BOTOX®) directly into the corrugator and procerus muscles, preventing them from contracting and eventually causing the skin to become smoother.
Additionally, use of RF energy when applied to the airways has been shown to decrease the ability of smooth muscle tissue to narrow the airways. Danek C J, et al, Reduction in Airway Hyperresponsiveness to Methacholine by the Application of RF Energy in Dogs. 2004 J Appl Physiol. Jul 16 doi:10.1152/japplphysio1.01282.2003 (electronic publication—ahead of print)
In view of the foregoing, there remains an additional need for removal and/or deactivation of certain types of muscle which may contribute to or cause an impaired quality of life. In just one specific example, there remains a need to remove and/or deactivate certain airway smooth muscle to address the effects of certain pulmonary conditions, including but not limited to asthma.